Neil Gee: Install and configure Apache, MySQL, PHP on OSX 10.8 Mountain Lion
Thats it you now have the native AMP stack running ontop of the Mountain Lion.
Sakuzaku: I Am Building Ruby, Rails, Subversion, Mongrel, and MySQL on Mac OS X -- Automatically (And So Can You!)
Like it says, a shell script to automatically install the perfect Ruby on Rails development environment on OS X. Useful!